The ETF2009 shootout was a contest of single-ended output transformers. Scroll down to see the results and pictures.
The test amplifier will be a 310A+300B "l'audiophile" (without negative feedback), and the speaker will have high sensitivity, passive crossover, more or less 8 ohm impedance.
The shootout listening tests will be MONOPHONIC : there is no need to bring a pair of identical transformers, one is enough.
The B+ voltage is about 430VDC, and the primary will have to handle 70mA DC.
The negative tap of the secondary will be joined to earth.
The impedance ratio can go from 2.2K / 8 ohm to 3.6K / 8 ohm.
The test amplifier has 4 female 4mm banana plug (IEC 1010 compatible) :
B+ (high voltage 430VDC) : Red
P (plate of the 300B) : Yellow
0 (earth of the amplifier, and negative input of the speaker) : Black
8 (positive input of the speaker) : White
How to register to the shootout ?
- First of all, you have to register to the triode festival : http://www.melaudia.net/subscribeETF.php
- On your registration form, fill the "participate to the shootout with" field with the name of your transformer (brand and reference, or any description if it is a DIY transformer)
- Bring one transformer with the cords+ 4mm banana plug at ETF
Participants are asked to :
Make sure that the transformer is not phase-inverting (but it is not disqualifying)
clearly identify each tap that plugs into the test amplifier (color and/or name)
provide 0.5 to 1m cords with 4mm male banana (IEC 1010 is recommanded)
Pay attention to insulation problems :
Before the shootout, the following tests will be performed :
- a 500V insulation test between B+ and 0 tap.
- turn ratio measurement.
- phase/out-of-phase check.
Special stuff :
Parafeed transformers (choke + condensator + transformer without air gap) are authorized.
DIY transformers are especially welcomed, but here again, pay attention to insulation.
mismatchs (5K to 16 ohm, used as 2.5K to 8 ohm, for instance) are authorized, but please indicate clearly which secondary tap you want to plug on the speakers, and which primary tap you want to use.
primary and/or secondary compensations are authorized (zobel network or whatever you want, providing it is not dangerous)
Sorry, negative feedback is forbidden.
Krell CD Transport and Wadia D/A converter
The WE310A+WE300B amplifier used for the shootout. There is no output transformer, but two sets of banana female plugs: B+ (red), 300B Plate (yellow), ground (black) and 8 ohm (white). A switch connects the transformer A or B.
The mono line preamp used for the shootout. Sowter multitap transformer for the volume, Tango output transformer (500 or 600 ohm external load).
A 10 turns 500 ohm potentiometer was used to calibrate the output level of each transformer. It is also the external load of the preamplifier.
The loudspeaker used for the shootout : Great Plain Audio 515 and 399, with Westrex acoustilens horn.
31 transformers ready for the shoot-out !!!
list of participants :
|29||Blöhbaum, Frank||PP output transformer, with one primary winding compensating the current of the 300B.|
|16||Dolinskyi, Arkadii||DIY EI transformer|
|15||Hasling, Per + Ole||SE Silk transformer from Tailand 3,0 kOhm|
|1||Højbjerg, Karsten||toroidal transformer in cardbox|
|24||Hubertse, Rob||custom made OPT by AE-Europe.|
|9||Michimori, Hirokuni||ex-Tango #10887 (special order), rating 50W, 3.5K/4,8,and16ohm,with 360hm KNFB winding|
|26||Monmagnon, Yves||Dissident audio transformer|
|14||Raudonat, Ralf||yes, with output transformer regarding the terms|
|18||Schwarz, Andreas||a selfmade single ended output transformer|
|2||Terrell, Brian||SE Output transformer|
|7||Veen, van der, Menno||toroidal SE-OPT's|
|11||Weidhase, Ulf||One Parafeed Transformer 3k5 /8 Ohm Transformer|
|23||Willenswaard, van, Peter||AudioNote Trans-300 double-C-core|
|19||Polisois, Aristide||DIY toroid transformer|
|13||DIY grey transformer|
|5||Falampin, Jérôme||Unknown semi-pro vintage transformer (in tea box)|
|3||Bouyer ST10 transformer (in soap box)|
|21||parafeed transformer (9H cheap chinese choke, 1µF cap, 50VA toroid power transformer 220V -> 12V) in biscuit box|
|25||Le Cléac'h, Jean-Michel||small and old Audionote classA|
|8||Magnetics (special order),|
|6||Sullerot, Julien||Partridge TK 4519|
|10||Tamura transformer from a Sun Audio 2A3 amp|
|28||Pierre-Francois Brand||Spanish transformer|
|27||Pierre-Francois Brand||R-core Softone RW-20 : http://www.icl.co.jp/audio/english/RW20.htm|
some pictures of the transformers :
Peter van Willenswaard (right) won with an Audionote Trans-300 double-C-core, and receives a pair of TJ 300B from Julien (left).
Jean-Michel measuring a transformer. Measurements (distortion, bandwidh, impulse response) have been made with 70mA through the primary.
See the measurements here .